KR102427122B1 - Method for reducing the optical reflectivity of a copper and copper alloy circuitry and touch screen device - Google Patents

Abstract

The present invention relates to a method for reducing the optical reflectance of copper and copper alloy circuits, wherein a thin layer of palladium or palladium alloy is deposited on the copper or copper alloy by immersion plating. Thereby, a matte gray or dark gray or black layer is obtained, and the optical reflectance of the copper or copper alloy circuit is reduced. The method according to the invention is particularly suitable for the manufacture of image display devices, touch screen devices and related electronic components.

Description

METHOD FOR REDUCING THE OPTICAL REFLECTIVITY OF A COPPER AND COPPER ALLOY CIRCUITRY AND TOUCH SCREEN DEVICE

FIELD OF THE INVENTION The present invention relates to methods for reducing optical reflectance of copper and copper alloy circuits in the manufacture of electronic components such as image display devices and touch screen devices.

Electrical circuits of electronic components such as image display devices and touch screen devices can be manufactured in different ways. The electrical circuit most often comprises copper or a copper alloy because of the high electrical conductivity of the material.

Such electrical circuits can be manufactured by, for example, physical vapor deposition (PVD) or chemical vapor deposition (CVD), such as sputtering, in which copper or a copper alloy is deposited on a dielectric substrate. Optionally, an adhesive layer, such as a titanium layer, a molybdenum layer or a multilayer stack comprising a titanium layer and a molybdenum layer, is first deposited on the substrate, and then copper or copper alloy, which is a major contributor to the electrical circuit, is deposited.

In another method of depositing an electrical circuit on a dielectric substrate in the manufacture of electronic components such as image display devices and touch screen devices, the electrical circuit is deposited by electroless plating of copper or copper alloy on a substrate activated with a noble metal. Such a method for electroless (autocatalytic) plating on substrates activated with noble metals is disclosed in EP 2 524 976 A1.

Electrical circuits of electronic components such as image display devices and touch screen devices can also be manufactured by an additional method in which a catalyst ink is deposited on a dielectric substrate material such as polyethylene terephthalate (PET) foil and then cured. The cured catalyst ink is then used as a plating base for electroless (autocatalytic) plating of copper and copper alloys. These additional copper or copper alloy layer(s) are generally required to achieve the required electrical conductivity for the circuit pattern, which is not normally achieved with cured catalyst inks alone. A process for the electroless plating of metals and metal alloys such as copper and copper alloys on cured catalyst inks is disclosed, for example, in EP 13188464.5.

In another manufacturing method, an electrical circuit is deposited by electroplating copper or a copper alloy to an electrically conductive pattern or layer attached to a dielectric substrate.

Irrespective of the method used to deposit the copper or copper alloy onto the substrate, one disadvantage of such copper or copper circuitry is that proprietary circuit pattern shapes, such as rectangular or hexagonal grids used in image display devices and touch screen devices, and e.g. It is the strong optical reflectivity of the glossy surface that results in optical visibility of the circuit despite very narrow circuit line widths of 50 μm, 20 μm, 10 μm or less.

Other methods are known in the prior art for reducing the optical reflectivity of copper and copper alloy surfaces in the manufacture of electronic components such as image display devices and touch screen devices.

A blackening procedure for copper circuits in the manufacture of electronic components such as such touch screen devices is disclosed in US 2013/0162547 A1, in which the copper surface is chemically oxidized to brown Cu ₂ O and black CuO. Thereby, the optical reflection of the copper circuit surface is reduced.

Another chemical oxidation procedure for copper circuits in the manufacture of electronic components such as touch screen devices is disclosed in US 2014/0057045 A1. In order to obtain a darkened copper surface and thereby reduce the optical reflectance of the copper circuit, the copper surface is treated with a chemical such as a selenium compound, a sulfate compound or a triazole compound.

A method for reducing the optical reflectivity of circuits made of silver is disclosed in US Pat. No. 7,985,527 B2. Silver is first blackened by a chemical oxidation treatment, and then the formed black silver oxide is stabilized by being contacted with a solution containing palladium ions or metal palladium.

A disadvantage of this chemical oxidation treatment disclosed in the prior art is the weak mechanical stability of such a surface oxide layer, which is brittle and has low adhesion to the underlying copper or silver surface. Therefore, such a blackened circuit lacks reliability.

Another disadvantage of such a chemical oxidation treatment is that copper in the circuit lines is consumed during the formation of copper oxide. Accordingly, a portion of the initial copper circuit is converted to electrically non-conductive copper oxide, and the resistivity of the copper circuit is increased after the formation of the copper oxide.

EP 0 926 263 A2 relates to a process for bonding resin layers to a roughened copper foil to form a multilayer printed circuit board. The process comprises microetching the copper foil, followed by a reducing agent and a metal selected from the group consisting of gold, silver, palladium, ruthenium, rhodium, zinc, nickel, cobalt, iron and alloys of these metals. contacting with an adhesion promoting composition. In one embodiment, an immersion palladium solution is used as an adhesion promoting layer with a micro etching solution. This method does not involve the formation of circuits. The purpose of the treatment is to provide a rough copper foil which is then laminated to the resin layer. The method according to EP 0 926 263 A2 results in the formation of a multilayer circuit board. It does not disclose the manufacture of copper circuits suitable for image display devices and touch screens. US 2008/0224314 A1 discloses the formation of a cap layer on a copper interconnect surface. The cap layer (see paragraph [0003]) may be Ni, Ni(P), Ni(Co) or Co(P). The cap layer serves to form a diffusion barrier and corrosion protection layer on the inlaid copper features (paragraph [0003]). It is proposed to deposit an "activation layer" such as palladium on the copper interconnect surface, which serves to facilitate subsequent deposition of other metals. US 2008/0224314 A1 does not disclose the formation of a copper or copper alloy circuit on which palladium or a palladium alloy is deposited as the outermost layer.

It is an object of the present invention to provide a method for reducing the optical reflectance of copper and copper alloy surfaces in the manufacture of electronic devices such as image display devices and touch screen devices having sufficient mechanical stability and low resistivity circuitry.

This object is solved by a method for reducing the optical reflectance of copper and copper alloy circuits, the method comprising the steps of:

(i) providing a dielectric substrate;

(ii) depositing copper or copper alloy on said dielectric substrate under the condition that said dielectric substrate includes a plating base when copper or copper alloy is deposited by electroless (autocatalytic) plating or electroplating; and

(iii) depositing a palladium or palladium alloy layer on the copper or copper alloy by immersion plating to reduce the optical reflectance of the copper or copper alloy;

include in this order,

The copper or copper alloy deposited in step (ii) is structured to form a circuit before or after step (iii).

The deposition and deposition of copper or copper alloy within the meaning of the present invention includes physical vapor deposition (PVD) or chemical vapor deposition (CVD), such as sputtering, electroless (autocatalytic) or electroplating, whereby copper or copper An alloy is deposited on the dielectric substrate.

The resulting copper or copper alloy circuit having a thin immersion plated palladium or palladium alloy layer deposited on the surface has a desired reduced optical reflectance compared to an untreated copper or copper alloy circuit, and has been subjected to oxidation treatments known in the prior art. has improved mechanical stability compared to the blackened copper or copper alloy surface obtained by Also, the corrosion resistance of the copper or copper alloy circuit is increased.

And, the immersion plated palladium or palladium alloy layer is very thin, meaning that only a small portion of the copper or copper alloy circuit is consumed during immersion plating. Accordingly, the electrical resistivity of such copper or copper alloy circuits is also as low as desired. The method of reducing the optical reflectance of copper and copper alloy surfaces is particularly suitable for the manufacture of electronic components such as image display devices and touch screen devices.

The present invention also provides a touch screen device comprising a copper or copper alloy circuit and a palladium or palladium alloy layer deposited on the copper or copper alloy circuit by immersion plating.

1 shows an image of a copper circuit (example 4) treated with a method according to the invention. FIB/SEM analysis was performed in an FEI Nova NanoLab 600 Dual Beam FIB. The region of interest in the FIB cut was sputter coated with carbon to obtain a good contrast to the underlying palladium. A second layer of platinum is applied over the carbon layer, which is necessary to perform FIB measurements.
2 shows an image of a copper circuit (example 3) treated with the method according to the invention. FIB/SEM analysis was performed on a FEI Nova NanoLab 600 Dual Beam FIB. The region of interest in the FIB cut was sputter coated with carbon to obtain a good contrast to the underlying palladium. A second layer of platinum is applied over the carbon layer, which is necessary to perform FIB measurements.

Suitable dielectric substrate materials for electronic components such as image display devices and touch screen devices include plastic materials and glass materials.

Examples of suitable plastic materials include polyethylene terephthalate (PET), polyacrylate, polyurethane (PU), epoxy resin, polyimide, polyolefin, polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylene naphthalate ( PEN), polyethersulfone (PES), cyclic olefin polymer (COC), triacetylcellulose (TAC), polyvinyl alcohol (PVA) and polystyrene (PS).

Examples of suitable glass materials include silica glass (amorphous silicon dioxide material), soda-lime glass, float glass, fluoride glass, aluminosilicate glass, phosphate glass, borate glass, borosilicate glass, chalcogenide glass, sapphire glass and glass-ceramic. includes materials.

The dielectric substrate material may be provided in the form of a rigid sheet or bendable foil.

Preferably, the dielectric substrate material is selected from an optically transparent material among a plastic material and a glass material. Electrical circuits made of copper or copper alloys can be deposited on dielectric substrates in different ways. The electrical circuit may be deposited directly in a desired pattern or the pattern may be formed after copper or copper alloy deposition by selectively removing a portion of the copper or copper alloy layer.

The deposition of the palladium or palladium alloy layer on the copper or copper alloy by immersion plating according to the method of the present invention may be after or before the desired pattern of the circuit is formed.

According to a first aspect of the present invention, the step (iii) of depositing a palladium or palladium alloy layer on copper or copper alloy by immersion plating is structured to form a circuit only after step (iii) (ii) It is performed on copper or copper alloy deposited in a film.

According to a second preferred embodiment of the present invention, the step (iii) of depositing a palladium or palladium alloy layer on the copper or copper alloy by immersion plating is structured to form a circuit before step (iii) (ii) It is performed on copper or copper alloy deposited in a film.

Copper and copper alloy circuits are formed by physical vapor deposition (PVD), chemical vapor deposition ( CVD), electroless (autocatalytic) plating, and electroplating.

In the first embodiment of the present invention, the electric circuit made of copper or copper alloy is directly deposited on the dielectric substrate by a deposition method such as PVD, CVD and related methods such as plasma-enhanced CVD. Such methods for the deposition of copper or copper alloys are known in the art.

In the second embodiment, an electric circuit made of copper or a copper alloy is deposited on an adhesive layer attached to a dielectric substrate by a deposition method such as PVD and CVD and related techniques.

Adhesive layer materials suitable for this second embodiment are, for example, molybdenum, titanium, zirconium, aluminum, chromium, tungsten, niobium, tantalum, the aforementioned alloys and multilayer stacks. Such an adhesive layer may also be deposited by deposition methods such as PVD and CVD and related methods.

In a third embodiment of the present invention, an electric circuit made of copper or a copper alloy is deposited on a dielectric substrate by electroless (autocatalytic) plating. A plating base is required over the dielectric substrate. Otherwise, autocatalytic plating of copper or copper alloys on dielectric substrates is not possible.

An electroless (autocatalytic) plating electrolyte is to be understood as a plating electrolyte that contains a chemical reducing agent and is used for autocatalytic plating.

In a fourth embodiment of the present invention, an electric circuit made of copper or a copper alloy is deposited by electroplating on an electrically conductive portion of a dielectric substrate, also referred to herein as a "plating base". Such electrically conductive portions may be, for example, metal or metal alloy layers deposited on a dielectric substrate by vapor deposition methods such as PVD, CVD and related techniques.

Other types of suitable plating bases for the electroplating of copper and copper alloys include electrically conductive polymers such as polythiophene, polypyrrole and polyaniline, as well as those described above that can be deposited on dielectric substrates, such as by dip coating or spin coating, embossing, or the like. is a derivative of

A conventional copper or copper alloy electroplating bath may be used to form an electrical circuit over a dielectric substrate. Suitable copper or copper alloy electroplating bath compositions are known in the art, such as "Modern Electroplating" (4th ed., Eds. M. Schlesinger and M. Paunovic, John Wiley & Sons, Inc., 2000, 61-103) page) is disclosed. A particularly suitable electroplating bath composition comprises a source of copper ions, an acid, an organic additive and halide ions.

The term "plating base" is used herein to initiate electroless (autocatalytic) plating of copper or copper alloys, including surfaces or parts of surfaces, preferably catalytically active metals, and/or continuous electroplating of copper and copper alloys. It is defined as a surface or part of a surface on a dielectric substrate that provides an electrically conductive material for

Suitable metals and metal alloys included in the plating base to initiate electroless (autocatalytic) plating of copper or copper alloys are also referred to herein as “catalytically active metals”.

Suitable catalytically active metals and metal alloys for the plating base allowing for initiating electroless (autocatalytic) plating of copper or copper alloys are, for example, copper, silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum, and these It is a mixture and alloy of The catalytically active metal or metal alloy may be provided, for example, in the form of ions, as a colloid, as metal particles embedded in a binder, and as a layer comprising such metal deposited by, for example, PVD, CVD and related techniques.

Accordingly, the plating base comprises a catalytically active metal that allows initiating electroless (autocatalytic) plating of copper or copper alloy, or an electrically conductive material that allows initiating electroplating of copper or copper alloy.

The plating base according to the present invention is also known in the art as "seed layer". The plating base or seed layer is distinct from the electrical circuit deposited thereon by the thickness of the plating base, which is much thinner than the copper or copper alloy layer used as the electrical circuit. Therefore, the plating base is not suitable for carrying the current required for a given electronic component. The thickness of the plating base is only a few nanometers, for example from 1 to 50 nm, whereas the thickness of the electrical circuit is preferably at least 500 nm or more to deliver the required amount of current of a given electronic component, such as a touch screen device. Even more than 1 μm.

Such a plating base may be deposited directly on the dielectric substrate or after modifying the surface of the dielectric substrate with, for example, an adhesive layer. Suitable adhesive layers for such catalytically active metals in ionic and colloidal form are, for example, nitrogen-containing materials and hydroxy carboxylic acids.

Metals such as molybdenum, titanium, zirconium, aluminum, chromium, tungsten, niobium, tantalum and their alloys provide very good adhesion of electrical circuits to plastic materials and glass materials, but the electroless (autocatalytic) of copper or copper alloys. Do not initiate plating. Thus, for these “non-catalytic” metals and metal alloys, activation with a catalytically active metal is required prior to electroless (autocatalytic) plating of copper or copper alloy.

A method for electroless (autocatalytic) plating of copper or a copper alloy onto an adhesive layer selected from molybdenum, titanium, zirconium, aluminum, chromium, tungsten, niobium, tantalum and alloys thereof is disclosed in EP 2 524 976 A1.

Suitable plating bases for the electroless (autocatalytic) plating of copper and copper alloys comprising catalytically active metals in ionic or colloidal form are described, for example, in ASM Handbook, Volume 5, Surface Engineering, 1194, p. 317-318.

Other types of plating bases suitable for electroless (autocatalytic) plating of copper or copper alloys and for electroplating of copper and copper alloys include metals deposited by PVD or CVD methods in the form of thin layers or patterns on dielectric substrates and It is a metal alloy. If the metal or metal alloy layer deposited as a plating base is catalytically active for electroless (autocatalytic) plating of copper or copper alloy, no further activation is required for electroless (autocatalytic) plating.

Another type of suitable plating base for electroless (autocatalytic) plating of copper and copper alloys is a binder material and a catalytically active metal or a mixture thereof or a precursor thereof, which is a fine metal or metal after deposition of a catalyst ink on a dielectric substrate. It is a catalyst ink containing particulates of the alloy).

Fine metal or metal alloy particles (or their precursors after activation) serve as a plating base for electroless (autocatalytic) plating of copper and copper alloys.

The "catalytically active metal" of the catalyst ink consists of fine particles of a metal and/or metal alloy that are catalytically active with respect to the metal or metal alloy to be deposited by electroless (autocatalytic) plating. Such catalytically active metals or metal alloys are known in the art. Suitable catalytically active metals are, for example, copper, silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum, mixtures and alloys thereof.

Suitable catalyst inks comprising catalytically active metal particles are disclosed, for example, in US Pat. No. 8,202,567 B2 and WO 2014/009927 A2.

The binder in the catalyst ink is preferably selected from an inorganic binder, a polymer binder and an inorganic-polymer mixed binder.

The catalyst ink may be deposited on the dielectric substrate by methods such as screen printing, embossing, inkjet printing, flexographic printing, gravure printing, offset printing, imprinting, and the like.

Curing of the catalyst ink after being deposited on the dielectric substrate refers to the process of drying, coagulating and fixing the catalyst ink to the dielectric substrate. Suitable curing methods are, for example, heating with an infrared heater, curing with an ultraviolet heater, curing with a laser, curing with a convection heater, and the like.

Next, a copper or copper alloy layer is deposited on the cured catalyst ink by electroless (autocatalytic) plating. A suitable method for the electroless (autocatalytic) plating of metals and metal alloys such as copper and copper alloys on cured catalyst inks is disclosed in EP 13188464.5.

Suitable electroless (autocatalytic) plating electrolytes for deposition of copper and copper alloys for all embodiments of the present invention include a copper ion source and optionally a second metal ion source, at least one complexing agent, at least one stabilizer additive. and reducing agents.

The concentration of copper ions is preferably 1 to 5 g/l.

The concentration of the at least one complexing agent is preferably between 5 and 50 g/l.

The concentration of the reducing agent is preferably 2 to 20 g/l.

The copper ion source is preferably selected from water-soluble copper salts and other water-soluble copper compounds.

The copper ion source is more preferably copper sulfate, copper chloride, copper nitrate, copper acetate, copper methane sulfonate, copper hydroxide; hydrates and mixtures of the foregoing.

The at least one complexing agent is preferably selected from the group consisting of carboxylic acids, polycarboxylic acids, hydroxycarboxylic acids, aminocarboxylic acids, alkanol amines and salts of the aforementioned acids.

The at least one complexing agent is more preferably polyamino monosuccinic acid, polyamino disuccinic acid, tartrate, N,N,N′,N′-tetrakis-(2-hydroxypropyl)-ethylenediamine, N′- (2-hydroxyethyl)-ethylenediamine-N,N,N'-triacetic acid, ethylenediamine-tetra-acetic acid, salts and mixtures thereof.

Preferred polyamino monosuccinic acids are ethylenediamine monosuccinic acid, diethylenetriamine monosuccinic acid, triethylenetetraamine monosuccinic acid, 1,6-hexamethylenediamine monosuccinic acid, tetraethylenepentamine monosuccinic acid, 2-hydroxypropylene-1, 3-diamine monosuccinic acid, 1,2-propylenediamine monosuccinic acid, 1,3-propylenediamine monosuccinic acid, cis-cyclohexanediamine monosuccinic acid, trans-cyclohexanediamine monosuccinic acid and ethylenebis(oxyethylenenitrilo) monosuccinic acid includes

Preferred polyamino disuccinic acids are ethylenediamine-N,N'-disuccinic acid, diethylenetriamine-N,N"-disuccinic acid, triethylenetetraamine-N,N"-disuccinic acid, 1,6-hexamethylenediamine N,N'-disuccinic acid, tetraethylenepentamine-N,N""-disuccinic acid, 2-hydroxypropylene-1,3-diamine-N,N'-disuccinic acid, 1,2 propylenediamine-N, N'-disuccinic acid, 1,3-propylenediamine-N,N"-disuccinic acid, cis-cyclohexanediamine-N,N'-disuccinic acid, transcyclohexanediamine-N,N'-disuccinic acid, and ethylene bis-(oxyethylenenitrile)-N,N'-disuccinic acid.

Suitable stabilizer additives for the electroless copper plating electrolyte include, for example, mercaptobenzothiazole, thiourea and its derivatives, various other sulfur compounds, cyanide and/or ferrocyanide and/or cobaltocyanide salts, polyethylene glycol derivatives, 2,2'-bipyridol, methylbutynol, and heterocyclic nitrogen compounds such as propionitrile. And molecular oxygen can also be used as a stabilizer additive by passing a uniform air stream through the copper electrolyte (ASM Handbook, Vol. 5: Surface Engineering, pp. 311-312).

Such plating bath compositions are preferably alkaline and optionally include alkaline substances such as sodium hydroxide and/or potassium hydroxide to achieve a desired pH value. The pH value of the electroless (autocatalyst) plating bath used in step (ii) of the process according to the invention is more preferably from 11 to 14, most preferably from 12.5 to 13.5.

The reducing agent is preferably selected from the group comprising formaldehyde, hypophosphite ion, glyoxylic acid, dimethylamine borane, borohydride and mixtures thereof.

Alternative sources for second metal ions (other than copper ions) are, for example, water-soluble compounds and water-soluble salts of metals such as nickel.

Preferred plating baths for electroless plating of copper and copper alloys are a source of copper ions and optionally a source of a second metal ion, a source of formaldehyde or glyoxylic acid as a reducing agent, and at least one polyamino disuccinic acid, or at least one polyamino succinic acid, or a mixture of at least one polyamino disuccinic acid and at least one polyamino monosuccinic acid, or tartrate, N,N,N',N'-tetrakis-(2-hydroxypropyl)- A mixture of ethylenediamine and N'-(2-hydroxyethyl)-ethylenediamine-N,N,N'-triacetic acid, or N,N,N',N'-tetrakis-(2-hydroxypropyl) - a mixture of ethylenediamine and ethylenediamine-tetra-astenic acid and a salt thereof as a complexing agent. It is particularly preferred that the complexing agent is combined with glyoxylic acid as a reducing agent.

The plating bath for electroless (autocatalytic) plating of copper and copper alloys is preferably carried out at a temperature in the range of 20 to 60 °C, more preferably 25 to 55 °C, most preferably 25 to 45 °C during step (ii). is maintained on

The dielectric substrate is preferably contacted with the electroless (autocatalytic) plating bath during step (ii) for 0.5 to 20 minutes, more preferably 1 to 15 minutes and most preferably 2 to 10 minutes. The plating time may be outside the above range, especially when a thin or thick copper or copper alloy layer is desired.

Thereby, a copper or copper alloy circuit having a copper-colored glossy surface and high optical reflectance is obtained.

The copper or copper alloy deposited in step (ii) is prepared before step (iii) or after step (iii), i.e., by depositing a palladium or palladium alloy layer on the copper or copper alloy by immersion plating to form the copper or copper alloy. is structured to form a circuit before or after reducing the optical reflectance of Methods for forming circuits from deposited copper or copper alloys are known in the art.

The electroless (autocatalytic) plating of copper or copper alloy to form an electric circuit in step (ii) is to be done in horizontal, reel-to-reel, vertical and vertical conveyor type plating equipment. can Such equipment is known in the art.

The electroplating of copper or copper alloy for forming an electric circuit in step (ii) may be performed in horizontal, reel-to-reel, vertical and vertical conveyor type plating equipment. Such equipment is known in the art.

The vapor deposition of copper or copper alloy in step (ii) of the method according to the invention can be done in standard equipment for PVD and CVD methods. Such equipment and suitable PVD and CVD methods are known in the art.

In one embodiment of the present invention, the copper or copper alloy circuit obtained in step (ii) is contacted with a conditioner solution comprising at least one phosphonate compound between steps (ii) and (iii). The optional conditioner solution is preferably an aqueous solution. The term "phosphonate compound" is defined herein as an organic compound containing a -C-PO(OH) ₂ group and/or a -C-PO(OR ₂ ) group, wherein R is substituted and unsubstituted alkyl; aryl and alkaryl.

This embodiment is particularly preferred when the immersion plating bath applied in step (iii) comprises a phosphonate compound.

More preferably, the at least one phosphonate compound is of formula (1)

selected from compounds according to

,

, 수소, 메틸, 에틸, 프로필 및 부틸로 이루어진 군으로부터 선택되고; R1 is

,

, hydrogen, methyl, ethyl, propyl and butyl;

,

,

, 수소, 메틸, 에틸, 프로필 및 부틸로 이루어진 군으로부터 선택되고, R2 is

,

,

is selected from the group consisting of hydrogen, methyl, ethyl, propyl and butyl,

,

, 수소, 메틸, 에틸, 프로필 및 부틸로 이루어진 군으로부터 선택되고, R3 is

,

is selected from the group consisting of hydrogen, methyl, ethyl, propyl and butyl,

,

, 수소, 메틸, 에틸, 프로필 및 부틸로 이루어진 군으로부터 선택되고, R4 is

,

is selected from the group consisting of hydrogen, methyl, ethyl, propyl and butyl,

n is an integer from 1 to 6; m is an integer from 1 to 6; o is an integer from 1 to 6; p is an integer of 1 to 6,

X is selected from the group consisting of hydrogen and a suitable counter ion. Suitable counterions are, for example, lithium, sodium, potassium and ammonium.

이고, More preferably, R1 and R3 are

ego,

이고, R2 is

ego,

이다.R4 is

to be.

Preferably, n, m, o and p are independently selected from 1 and 2. More preferably, n, m are 1; o and p are 2.

The at least one phosphonate compound in the optional conditioner solution is most preferably 1-hydroxyethane-1,1,-diphosphonic acid, hydroxyethyl-amino-di-(methylene phosphonic acid), carboxymethyl- Amino-di-(methylene phosphonic acid), amino-tris-(methylene phosphonic acid), nitrilo-tris-(methylene phosphonic acid), ethylenediamine-tetra-(methylene phosphonic acid), hexamethylenediamino-tetra-( methylene phosphonic acid), N-(phosphonomethyl) imidodiacetic acid, diethylenetriamine-N,N,N',N",N"-penta-(methylphosphonic acid), 2-butane phosphonate 1, 2,4-tricarboxylic acid, ethane-1,2-bis-(iminobis-(methylphosphonic acid)) and 2-phosphonobutane-1,2,4-tricarboxylic acid.

The concentration of the at least one phosphonate compound in the optional conditioner solution is preferably from 0.3 to 20 mmol/l, more preferably from 0.3 to 20 mmol/l, even more preferably from 0.3 to 8 mmol/l.

The dielectric substrate is optionally contacted with an acidic aqueous solution between steps (ii) and (iii). The acidic aqueous solution preferably has a pH value of 0.5 to 2 and contains sulfuric acid. Such treatment of the copper surface is for cleaning, not for etching purposes. For this reason, in the cleaning process between steps (ii) and (iii) according to the present invention, a so-called micro-etching solution containing an oxidizing agent for etching and removing copper from the surface is generally not used.

The surface of the copper or copper alloy deposited in step (ii) of the method according to the present invention is cleaned when using said acidic aqueous solution between steps (ii) and (iii) and forming a film of palladium or palladium alloy (step (iii) )) is more suitable for

Next, a palladium or palladium alloy layer is deposited on the surface of the copper or copper alloy obtained in step (ii) of the method according to the present invention by immersion plating.

A dielectric substrate comprising copper or copper alloy is contacted with an immersion plating bath. Thereby, a thin layer of palladium or a palladium alloy is deposited on the surface of the copper or copper alloy.

In the immersion reaction according to the present invention, palladium ions are reduced by the deposited copper or copper of the copper alloy to form a reduced metallic palladium film on the surface of the copper or copper alloy. In turn, metallic copper from the copper or copper alloy surface is oxidized to form copper ions that are dissolved in the immersion plating solution. This type of reaction is selective, ie the palladium or palladium alloy deposition takes place only on copper or copper alloy.

The deposition of immersion palladium or palladium alloy onto copper or copper alloy in step (iii) may follow two embodiments:

1. The copper or copper alloy deposited in step (ii) is structured to form a circuit prior to depositing the palladium or palladium alloy in step (iii). In this embodiment, the palladium or palladium alloy is selectively deposited only on the copper or copper alloy circuit.

2. The copper or copper alloy deposited in step (ii) is structured to form a circuit after depositing the palladium or palladium alloy in step (iii). In this embodiment, palladium or a palladium alloy is deposited over the entire surface of the copper or copper alloy. Only after that, the copper is structured to form the corresponding circuit. In this embodiment, the palladium is also removed from the surface by the structuring method along with the copper or copper alloy.

The color of the copper or copper alloy is determined by the thickness of the palladium or palladium alloy deposited on the copper or copper alloy circuit by the treatment according to step (iii) of the method of the present invention, the composition of the immersion plating bath, and the plating bath temperature during plating. Depending on the same plating parameters, it changes from shiny copper color to dull gray or matt dark gray or matte black. Thereby, the optical reflectance of the copper or copper alloy is reduced.

The color of the obtained palladium or palladium alloy deposit can be measured by a colorimeter, and the color is L* a* b* color space system (introduced in 1976 by Commission Internationale de I'Eclairage) is described by Values L* represent brightness and a* and b* represent color directions. Positive values of a* indicate red, while negative values of a* indicate green. A positive value of b* means yellow, and a negative value of b* means blue. As the absolute values of a* and b* increase, the color saturation also increases. The value of L* ranges from 0 to 100, where 0 means black and 100 means white. Therefore, in the case of the palladium or palladium alloy deposits of the present invention, a low L* value is desirable.

The absolute value varies depending on the specific technical application. In general, the optical reflectivity of the surface of the treated copper or copper alloy is tuned according to the type of application and the reflectivity of the surrounding substrate surface.

The L* value of the copper surface prior to treatment with a palladium immersion solution is generally in the range of 50 or higher. After treatment, the L* value is greatly reduced in the range from 10 to 40, or preferably from 20 to 35. Therefore, after the deposition of palladium or palladium alloy, the color of copper or copper alloy is matte gray or matt dark gray or matte black.

The b* value of the dark palladium deposit of the present invention is in the range of -15.0 to +15.0. Accordingly, the dark color tone of the dark palladium deposit of the present invention is from yellow or brown to blue or gray.

The a* value of the dark palladium deposit of the present invention is in the range of -10.0 to +10.0. Therefore, the dark color tone of the dark palladium deposit of the present invention is hardly affected by the a* value, and a small deviation of a* within the color of the dark palladium deposit is not visible to the naked eye. Table 1 shows the L*, a* and b* values of the palladium deposits prepared by the method of the present invention.

The thickness of the palladium or palladium alloy layer is preferably from 1 to 300 nm, more preferably from 10 to 200 nm, even more preferably from 25 to 100 nm, most preferably from 30 to 60 nm. Thereby, compared to the blackening method of forming copper oxide on the surface of copper or copper alloy, a desired reduction in optical reflectance is obtained and at the same time less copper is oxidized (and less lost as an electrically conductive part of the copper or copper alloy circuit).

A suitable immersion plating bath composition for depositing a palladium or palladium alloy layer on the copper or copper alloy comprises at least one solvent and a palladium ion source.

During immersion plating, copper and other metals are oxidized in the case of a copper alloy, and palladium and other metals are reduced to a metallic state in the case of a palladium alloy and deposited on the outer surface of the copper or copper alloy. This plating mechanism distinguishes the immersion plating from electroless (autocatalytic) plating using, for example, a chemical reducing agent in a plating bath, and electroplating using an external current applied to at least one anode and an electrically conductive portion of the substrate.

The immersion plating bath used in step (iii) of the method of the present invention is preferably an acid plating bath, more preferably the plating bath has a pH value of 0.5 to 4, most preferably 1 to 2.

The palladium ion source in the immersion plating bath is selected from water-soluble palladium salts and water-soluble palladium complexes. Suitable water-soluble palladium salts are, for example, palladium sulfate, palladium acetate, palladium nitrate, palladium chloride and palladium perchlorate. Suitable water-soluble palladium complexes are, for example, complexes of palladium(II) ions with an alkylamine such as ethylene-diamine and a counterion such as sulfate, nitrate, and the like.

The concentration of palladium ions in the immersion plating bath is preferably 0.01 to 1 g/l, more preferably 0.05 to 0.3 g/l.

The solvent of the immersion plating bath is preferably water.

The immersion plating bath used in step (iii) of the process according to the invention preferably further comprises an acid. Suitable acids are, for example, sulfuric acid, sulfonic acid, carboxylic acid and mixtures thereof.

If the pH value of the immersion plating bath is too low, it may be increased by adding an alkaline substance such as sodium hydroxide or potassium hydroxide aqueous solution to obtain a desired pH value.

The immersion plating bath preferably further comprises at least one phosphonate compound defined herein as an organic compound containing -C-PO(OH) ₂ and/or -C-PO(OR) ₂ groups, , wherein R is selected from the group comprising substituted and unsubstituted alkyl, aryl and alkaryl.

More preferably, the at least one phosphonate compound is of formula (1)

selected from compounds according to

,

, 수소, 메틸, 에틸, 프로필 및 부틸로 이루어진 군으로부터 선택되고; R1 is

,

, hydrogen, methyl, ethyl, propyl and butyl;

,

,

, 수소, 메틸, 에틸, 프로필 및 부틸로 이루어진 군으로부터 선택되고, R2 is

,

,

is selected from the group consisting of hydrogen, methyl, ethyl, propyl and butyl,

,

, 수소, 메틸, 에틸, 프로필 및 부틸로 이루어진 군으로부터 선택되고, R3 is

,

is selected from the group consisting of hydrogen, methyl, ethyl, propyl and butyl,

,

, 수소, 메틸, 에틸, 프로필 및 부틸로 이루어진 군으로부터 선택되고, R4 is

,

is selected from the group consisting of hydrogen, methyl, ethyl, propyl and butyl,

n is an integer from 1 to 6; m is an integer from 1 to 6; o is an integer from 1 to 6; p is an integer of 1 to 6,

X is selected from the group consisting of hydrogen and a suitable counter ion. Suitable counterions are, for example, lithium, sodium, potassium and ammonium.

이고, More preferably, R1 and R3 are

ego,

이고, R2 is

ego,

이다.R4 is

to be.

Preferably, n, m, o and p are independently selected from 1 and 2. More preferably, n, m are 1; o and p are 2.

The optional at least one phosphonate compound in the immersion plating bath is 1-hydroxyethane-1,1,-diphosphonic acid, hydroxyethyl-amino-di-(methylene phosphonic acid), carboxymethyl-amino-di -(methylene phosphonic acid), amino-tris-(methylene phosphonic acid), nitrilo-tris-(methylene phosphonic acid), ethylenediamine-tetra-(methylene phosphonic acid), saxamethylenediamino-tetra-(methylene phosphonic acid) ), N-(phosphonomethyl) imidodiacetic acid, diethylenetriamine-N,N,N',N",N"-penta-(methylphosphonic acid), 2-butane phosphonate 1,2,4 Most preferably selected from the group comprising -tricarboxylic acid, ethane-1,2-bis-(iminobis-(methylphosphonic acid)) and 2-phosphonobutane-1,2,4-tricarboxylic acid.

The concentration of the optional one or more phosphonate compounds in the immersion plating bath is preferably from 0.3 to 20 mmol/l, more preferably from 1.5 to 8 mmol/l.

The optical reflectance of a copper or copper alloy circuit is even further reduced when depositing a palladium or palladium alloy layer from an immersion plating bath comprising at least one of the aforementioned phosphonate compounds (Example 4). Surprisingly, further investigations have shown that a palladium-copper alloy is obtained from an immersion plating bath comprising at least one phosphonate compound. The color of the palladium-copper alloy layer is much darker than the matte gray or matte dark gray of the palladium layer obtained from an immersion plating bath containing no such phosphonate compound. Accordingly, when an immersion plating bath comprising at least one phosphonate compound is used, the optical reflectance of the surface of copper or copper alloy is further reduced.

Without wishing to be bound by theory, Applicants believe that the addition of phosphonate compounds affects the immersion deposition mechanism of palladium or palladium alloys on copper or copper alloys. The film formation in the presence of a fossil not compound can be more controlled and the voids that often occur in the underlying metal layer can be much reduced. In this case, the exchange reaction between palladium and copper when using the phosphonate additive results in fewer voids in the copper or copper alloy. This is demonstrated in the examples.

Also, a more controlled mechanism in the presence of a phosphonate compound allows better control of the color of the palladium or palladium alloy layer to reduce the optical reflectivity of the copper or copper alloy.

Other optional components of the immersion plating bath are, for example, surfactants, sources of halide ions such as NaCl, complexing agents and buffering agents for palladium ions.

Suitable complexing agents for palladium ions as an optional component of the immersion plating bath are selected from the group comprising primary amines, secondary amines and tertiary amines. Suitable amines are for example ethylene-diamine, 1,3-diamino-propane, 1,2-bis (3-amino-propyl-amino)-ethane, 2-diethyl-amino-ethyl-amine, diethylene-triamine , diethylene-triamine-penta-acetic acid, nitro-acetic acid, N-(2-hydroxy-ethyl)-ethylene-diamine, ethylene-diamine-N,N-diacetic acid, 2-(dimethyl-amino)-ethyl -amine, 1,2-diamino-propyl-amine, 1,3-diamino-propyl-amine, 3-(methyl-amino)-propyl-amine, 3-(dimethyl-amino)-propyl-amine, 3 -(diethyl-amino)-propyl-amine, bis-(3-amino-propyl)-amine, 1,2-bis-(3-amino-propyl)-alkyl-amine, diethylene-triamine, triethylene -tetramine, tetra-ethylene-pentamine, penta-ethylene-hexamine and mixtures thereof.

When a palladium alloy is deposited in step (iii) of the method according to the present invention, the immersion plating bath further comprises a source for metal ions of a metal other than palladium. A suitable metal to be deposited with palladium in step (iii) is, for example, copper. Copper ions present in the immersion plating bath may be derived from an immersion plating reaction with a copper or copper alloy circuit, reduced and re-deposited with palladium on the copper or copper alloy circuit to form a palladium-copper alloy .

Copper ions can be added to the immersion plating bath used in step (iii) of the method according to the invention in the form of a water-soluble copper salt and/or a water-soluble copper compound such as copper sulfate to obtain a palladium-copper alloy layer. . The concentration of copper ions is preferably 50 to 100 mg/l.

The palladium-copper alloy is preferably the palladium alloy deposited in step (iii) of the present invention because this alloy has a particularly dark matte appearance. Accordingly, the optical reflectivity of the copper or copper alloy circuit is reduced much more than in the case of pure palladium deposited on the copper alloy or copper circuit.

The term “alloy” is defined herein as intermetallic compounds, intermetallic phases and intermetallic deposits comprising individual palladium and alloying element(s) domains.

The immersion plating bath is preferably maintained at a temperature of from 20 to 60°C, more preferably from 20 to 40°C during step (iii) of the process according to the invention.

A substrate comprising copper or a copper alloy is contacted with the immersion plating bath during step (iii), preferably for 20 to 180 s, more preferably 30 or 45 to 120 s.

The substrate comprising copper or copper alloy may be contacted with the immersion plating bath applied in step (iii) of the present invention, for example in horizontal, reel-to-reel, vertical and vertical conveyor plating equipment. Such installations are known in the art.

Preferably, no further metal or metal alloy layer is deposited on the palladium or palladium alloy layer obtained in step (iii) of the method according to the invention. In this embodiment, the palladium or palladium alloy layer forms the outermost metal layer of the copper or copper alloy circuit.

Yes

The present invention will now be described with reference to the following non-limiting examples.

General procedure:

PET stripes having a size of 30×40 mm 2 and containing a pattern of curing catalyst ink as a plating base were used in all examples. The line width of the patterned catalyst ink was 4 to 12 μm.

Copper was deposited onto the curing catalyst ink from an electroless (autocatalytic) plating bath containing a source of copper ions, formaldehyde as a reducing agent, and tartrate as a complexing agent. The plating bath temperature was maintained at 35° C. during plating, and the plating time was 6 minutes.

L*, a* and b* values were determined by statistical evaluation of light microscopy images. All values are based on 4 measurements per image with more than 3000 pixels per measurement.

Example 1 ( comparative example )

No palladium or palladium alloy layer was deposited on the copper circuit deposited by electroless (autocatalytic) plating.

Thus, the copper circuit had a glossy copper colored surface with undesirably high optical reflectivity (see Table 1 for color values).

Example 2 ( comparative example )

A copper circuit formed by electroless (autocatalytic) plating was subjected to a “blackening” treatment according to US 2013/0162547 A1. The copper circuit was brought into contact with an aqueous solution containing sodium hydroxide and sodium chlorite to form black copper oxide on the surface of the copper circuit.

Although the optical reflectance of the copper surface was reduced, the black copper oxide coating could be wiped off with a white towel. Therefore, the adhesion of the blackening layer on the copper circuit was not sufficient.

Example 3

A palladium layer was deposited on the copper layer from a plating bath composed of water, palladium sulfate and sulfuric acid by immersion plating.

A matte gray deposit with sufficient adhesion was obtained, and the optical reflectance of the copper surface was reduced by the above treatment.

The values according to the coloring mode are shown in Table 1 for different treatment times (30 sec, 60 sec and 90 sec). It can be seen that the colorant remains approximately constant over various treatment times.

2 shows a FIB (Focused Ion Beam) image of a copper circuit processed according to the method of the present invention. A non-uniform palladium layer having a thickness of about 100 nm is formed on the copper layer. Some voids were formed by the immersion exchange reaction in the copper circuit. The amount of voids should be as low as possible, but still acceptable for technical applications of the present invention.

Example 4

A uniform palladium layer was deposited by immersion plating on the copper layer from an aqueous plating bath composed of water, palladium sulfate, sulfuric acid and a phosphonate compound (amino-tris(methylene phosphonic acid)).

A matt dark gray deposit with sufficient adhesion was obtained, and the above treatment reduced the optical reflectance of the copper surface much more than in the absence of a phosphonate compound (Example 3).

The values according to the coloring mode are shown in Table 1 for different treatment times (30 sec, 60 sec and 90 sec). It can also be seen that the coloration varies with various processing times and can be adjusted according to the desired application. This better control is due to the phosphonate additive in the immersion palladium solution.

1 shows a FIB (Focused Ion Beam) image of a copper circuit processed according to the method of the present invention. A palladium layer having a thickness of about 100 nm is formed over the copper layer. The amount of voids is much lower when using the submerged composition according to Example 4 (containing phosphonate additive) compared to Example 3 ( FIG. 2 ).

Claims (16)

A method of reducing optical reflectance of copper and copper alloy circuits by depositing a metal layer of palladium or a palladium alloy on the copper and copper alloy circuits, the method comprising:
(i) providing a dielectric substrate;
(ii) depositing copper or copper alloy on said dielectric substrate under the condition that said dielectric substrate includes a plating base when copper or copper alloy is deposited by autocatalytic electroless plating or electroplating; and
(iii) depositing a palladium or palladium alloy layer on the copper or copper alloy by immersion plating to reduce the optical reflectance of the copper or copper alloy;
include in this order,
the copper or copper alloy deposited in step (ii) is structured to form a circuit before or after step (iii);
characterized in that the palladium or palladium alloy is deposited in step (iii) from an aqueous plating bath comprising a palladium ion source, an acid and at least one phosphonate compound,
A method for reducing optical reflectance in a copper and copper alloy circuit, wherein palladium ions are reduced by the copper or copper alloy in the immersion plating. The method of claim 1,
A method of reducing optical reflectance in copper and copper alloy circuits, characterized in that the copper or copper alloy deposited in step (ii) is structured to form a circuit prior to step (iii). The method of claim 1,
wherein the copper or copper alloy deposited in step (ii) is structured to form a circuit after step (iii). The method of claim 1,
A method for reducing optical reflectance of copper and copper alloy circuits, characterized in that the palladium or palladium alloy layer formed in step (iii) is an outermost metal layer. The method of claim 1,
wherein the dielectric substrate is selected from the group consisting of a glass material and a plastic material. The method of claim 1,
wherein the copper or copper alloy is deposited by autocatalytic electroless plating from a plating bath comprising a copper ion source, a reducing agent, at least one complexing agent and at least one stabilizer additive. How to reduce the optical reflectance of a circuit. The method of claim 1,
Copper and copper alloys, characterized in that the plating base comprises a catalytically active metal for initiating autocatalytic electroless plating of copper or copper alloy or an electrically conductive material for initiating electroplating of copper or copper alloy. How to reduce the optical reflectance of a circuit. delete delete The method of claim 1,
The at least one phosphonate compound is of formula (1)

is selected from the group comprising a compound according to
R1 is

,

, hydrogen, methyl, ethyl, propyl and butyl;
R2 is

,

,

is selected from the group consisting of hydrogen, methyl, ethyl, propyl and butyl,
R3 is

,

is selected from the group consisting of hydrogen, methyl, ethyl, propyl and butyl,
R4 is

,

is selected from the group consisting of hydrogen, methyl, ethyl, propyl and butyl,
n is an integer from 1 to 6; m is an integer from 1 to 6; o is an integer from 1 to 6; p is an integer of 1 to 6,
X is selected from the group consisting of hydrogen, lithium, sodium, potassium and ammonium. The method of claim 1,
A method for reducing optical reflectance in copper and copper alloy circuits, characterized in that the concentration of said at least one phosphonate compound is between 0.15 and 20 mmol/l. The method of claim 1,
A method for reducing optical reflectance of copper and copper alloy circuits, characterized in that the pH value of the plating bath used in step (iii) is 0.5 to 4.0. The method of claim 1,
A method for reducing optical reflectance of copper and copper alloy circuits, characterized in that the palladium alloy deposited in step (iii) is a palladium-copper alloy. An immersion-type palladium or palladium alloy layer obtained by the method according to any one of claims 1 to 7 and 10 to 13 for use in reducing the optical reflectivity of a copper or copper alloy circuit. 15. The method of claim 14,
and the optical reflectance is reduced by 30 to 80% of the initial optical reflectance of the copper or copper alloy circuit. 14. A copper or copper alloy circuit and an immersion method obtained by the method according to any one of claims 1 to 7 and 10 to 13 on said copper or copper alloy circuit. A touch screen device comprising a palladium or palladium alloy layer.

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